Systems and methods for managing conditions in enclosed space

ABSTRACT

Systems and methods for controlling temperature in an enclosed space can include an air-to-air heat exchanger (AAHX) and a direct evaporative cooler (DEC). The DEC can be located in a scavenger or outdoor air stream such that the DEC cools the outdoor air, which is then used to cool or reject heat from a process air stream passing through the AAHX. In an example, the AAHX can be a sensible wheel. In another example, the AAHX can be a counter-flow flat plate. The system can operate in various modes, including an economizer mode and an evaporation mode, depending, in part, on the outdoor air conditions and a load on the system. In some examples, the system can include a DX coil to provide additional cooling to the process air in another operating mode.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent applicon Ser. No.14/744,950, filed Jun. 19, 2015, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/014,985, filed on Jun. 20,2014, and also claims the benefit of U.S. Provisional Patent ApplicationSer. No. 62/027,050, filed on Jul. 21, 2014, the benefit of priority ofeach of which is claimed hereby, and each of which are incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present patent application relates to heating and cooling, and moreparticularly, to cooling systems and methods for cooling an enclosedspace, including, for example, a data center.

BACKGROUND

There are many applications for which controlling the environmentalconditions within an enclosed space is important—for example, coolingdata centers. A data center usually consists of computers and associatedcomponents operating 24 hours a day, 7 days a week. The electricalcomponents in data centers produce a lot of heat, which needs to beremoved from the space. Air-conditioning systems in data centers canconsume as much as 40% of the total energy.

There are several methods to reduce the air-conditioning system's energyconsumption in cooling only applications such as data centers,including, for example, conventional evaporative/adiabatic coolers,including indirect/hybrid designs for space cooling. Two general methodscurrently used are air-side economizers and water-side economizers. Theair-side economizer runs outdoor air into the data center wheneveroutdoor air conditions are suitable to reject the heat from the datacenter. Using the air-side economizer can increase the risk of dustaccumulation and air contaminants inside the space and may be limited torelatively cold and dry climates. The water-side economizer is usually acooling tower which cools some or all of the return water in a chilledwater loop. Water mineral deposition, micro-organisms and biofilm growth(e.g. Legionella bacteria), corrosion of metal components and othermaintenance challenges in the tower are some of the drawbacks for thewater-side economizer. Also, the water-side economizer application maybe limited to relatively hot and dry climates.

Another recent cooling method is using direct evaporative coolers (DEC)to cool buildings and other enclosed spaces. Conventional directevaporative coolers, although typically more energy efficient than vaporcompression systems, have some drawbacks. The supply air temperaturecoming out of the cooler may be challenging to control and is dependenton the outdoor air temperature and humidity level. The supply air may beexcessively humid. These systems need careful maintenance to ensure thatbacteria, algae, fungi and other contaminants do not proliferate in thewater system and transfer into the supply air stream. Since thesesystems utilize direct contact between the evaporating liquid water andsupply air, carryover of contaminants into the air stream can occur,which can, in turn, lead to reduced indoor air quality, odors and “sickbuilding syndrome.” Also, buildup of mineral deposits in the unit and onthe evaporative pads can reduce performance and require maintenance.

In addition to maintenance challenges, direct and indirect evaporativecoolers are typically limited to cooling temperatures no lower than thewet bulb temperature of the air stream travelling through theevaporative device. For example, if an indirect evaporative cooler usesoutdoor scavenging air, the cooler may fail to meet the required coolingtemperatures or handle the sensible load of a building space wheneverthe outside air wet bulb temperature becomes too high. This may limitthe range of climate conditions suitable for the evaporative coolingtechnology, or necessitate the use of back up chillers whenever theevaporative system loses capacity. Redundant cooling equipment furtherincreases the cost and complexity of the system.

Overview

The present inventors recognize, among other things, an opportunity forimproved performance in providing cooling to an enclosed space using acombination of a direct evaporative cooler (DEC) in a scavenger airstream and an air-to-air heat exchanger exchanging heat between thescavenger air stream and a process air stream.

The following non-limiting examples pertain generally, but not by way oflimitation, to systems and methods for cooling an enclosed space,including, for example, a data center. The following non-limitingexamples are provided to further illustrate the systems and methodsdisclosed herein.

Examples according to this disclosure include an integrated sensiblewheel, or other type of air-to-air heat exchanger (AAHX), and a directevaporative cooler (DEC) to indirectly and sensibly cool process air. Apre-cooler coil may be included upstream of the DEC to achieve coolingtemperatures below the outdoor air wet-bulb temperature. A directexpansion (DX) cooling system with an air-cooled or water-cooledcondenser may also be included to achieve a target cold aisle supplytemperature in relatively hot and humid climates. The proposed systemsand methods may improve on performance, packaging and price of existingdirect/indirect evaporative cooling/hybrid systems in the market fordata center (and other enclosed space) cooling.

Although some of the following examples are described in the context ofcooling data centers, examples according to this disclosure, includingthe combination of a sensible wheel and DEC, can be employed to controlother environmental conditions within other types of enclosed spaces.

Using the proposed system, which is an air-to-air heat exchanger (AAHX)in combination with a direct evaporative cooler (DEC) in a scavenger airstream, a number of advantages may be realized. In examples, a sensiblewheel is combined with a DEC to deliver improved performance over othertypes of AAHXs (such as, heat pipe, glycol run-around loop andcross-flow flat-plate AAHX) for cooling applications (such as datacenter cooling). In examples, a counter-flow AAHX is combined with a DECto deliver improved performance. Such example systems and methods mayprovide a number of advantages over conventional evaporative/hybridcooling systems as outlined in more detail below. The proposed systemindirectly cools the process air from the enclosed space, which canreduce the risk of dust accumulation and outdoor air contaminanttransfer to the space. Thus, the proposed system may significantlyreduce the air filtration required for alternative cooling systems.Also, the proposed system sensibly cools the process air, which canprovide better humidity control for enclosed spaces such as datacenters.

Examples according to this disclosure can be used for both roof-top andend-on delivery applications, which can expand applicability of suchsystems and methods to different market conditions. Some examplesdescribed below include integration of a supplementary mechanicalcooling system (e.g., direct expansion, or “DX” cooling system) with anair-cooled/water cooled condenser, along with the sensible wheel and DECsystem, to provide further cooling to the process air, as necessary.Using the cold water of the DEC, which is at the scavenger air wet-bulbtemperature, in the water-cooled condenser can boost the DX coolingsystem and overall system performance.

Example systems and methods may also allow an evaporative system toachieve cooling temperatures lower than the scavenging air wet bulbtemperature using a pre-cooler upstream of the direct evaporative cooler(DEC). This expands the operating range of the evaporative cooler andmay eliminate the need for back-up chillers or other equipment (i.e. abackup DX cooling system) in many climates. In addition, variousproposed configurations of components and airflow paths may improve theoverall system efficiency, flexibility and potential forcommercialization in a number of different markets compared to otherevaporative technologies.

This overview is intended to provide an overview of subject matter ofthe present patent application. It is not intended to provide anexclusive or exhaustive explanation of the invention. The detaileddescription is included to provide further information about the presentpatent application.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 2 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 3 is a schematic of an example direct expansion (DX) system for usein a roof-top or end-on delivery system in accordance with the presentpatent application.

FIG. 4 is a schematic of an example direct evaporative cooler (DEC) foruse in a roof-top or end-on delivery system in accordance with thepresent patent application.

FIG. 5 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 6 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 7 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 8 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 9A is a schematic of an end view of an example end-on deliverysystem in accordance with the present patent application.

FIG. 9B is a schematic of a side view of the end-on delivery system inFIG. 9A.

FIG. 10 is a side view of an example roof-top system in accordance withthe present patent application.

FIG. 11 is a schematic of a bottom view of the roof-top system of FIG.10.

FIG. 12 is a schematic of a top view of the roof-top system of FIG. 10.

FIG. 13 is a graph illustrating the impact of sensible performance of anair-to-air heat exchanger (AAHX) on an overall system performance.

FIG. 14 is a graph illustrating the impact of sensible performance of anAAHX on an outdoor air wet bulb (OAWB) limit.

FIG. 15 is a schematic of an example roof-top system in accordance withthe present patent application.

FIG. 16 is a schematic of an example roof-top system in accordance withthe present patent application.

DETAILED DESCRIPTION

The present application relates to systems and methods for controllingconditions, such as temperature, inside an enclosed space, such as, forexample, a data cooling center. The system can include a directevaporative cooler (DEC) in combination with an air-to-air heatexchanger (AAHX). The DEC can be located in an outdoor or scavenger airstream and used to cool the scavenger air, which, in turn, cools theprocess air in the AAHX. The system can include roof-top or end-ondelivery applications.

FIG. 1 depicts an example roof-top system 100 including a sensible wheel102 and a direct evaporative cooler (DEC) 104. FIG. 4 illustrates anexample of a DEC configured for use in the roof-top system 100 and isfurther described below. The sensible wheel 102 is an example of anair-to-air heat exchanger (AAHX) which can be used in combination withthe DEC 104. The system 100 of FIG. 1 is a two-level unit, in which thescavenger air stream flows through a top level 106 and the process airstream flows through a bottom level 108. The scavenger air stream, oroutdoor air, enters the top level 106 through a scavenger air inlet 110and exits the top level 106 through a scavenger air outlet 112. Theprocess air stream, from a data center, for example, enters the bottomlevel 108 at a process air inlet 114 as hot aisle return air and exitsthe bottom level 108 at a process air outlet 116 as cold aisle supplyair.

The scavenger air inlet 110 and outlet 112, as well as the process airinlet 114 and outlet 116, can be configured as dampers such that theinlets and outlets can be open or shut to allow or prevent air flow.

On the top level 106, the system 100 can include a filter 118 before theDEC 104, a fan 120 after the sensible wheel 102, and a bypass damper 122between the DEC 104 and the sensible wheel 102. On the bottom level 108,the system 100 can include a filter 124 before the sensible wheel 102and a fan 126 after the sensible wheel 102. It is recognized that thesystem 100 can include more or less fans and filters than what is shownin FIG. 1 and some or all of the fans and filters may be optional.Moreover, the fans and filters can be located in different locationswithin the system 100 relative to what is shown in FIG. 1. The fan 120in the top level 106 or the fan 126 in the bottom level 108 can beconfigured as a single fan or multiple fans, including a fan array, suchas, for example, FANWALL® Systems provided by Nortek Air Solutions. Thedescription in this paragraph about the fans and filters can apply tothe other systems, including roof-top or end-on applications, describedherein.

In one example, the system 100 of FIG. 1 can operate in at least twomodes—an evaporation mode and an economizer mode. In an evaporationmode, the scavenger air enters the unit at the inlet 110 and passesthrough the DEC 104 and is cooled to its wet-bulb temperature. Thescavenger air then passes through the sensible wheel 102 and indirectlycools the process air in the bottom level 108, which is also passingthrough the sensible wheel 102. The scavenger air exiting the system 100at the scavenger air outlet 112 is at a higher temperature and humiditysince it has been used to cool the process air passing through thesensible wheel 102. The process air exiting the system 100 at theprocess air outlet 116 is thus at a lower temperature compared to at theprocess air inlet 114 and can be supplied to wherever the cooler air isneeded. In an example, the process air can be supplied back to the datacenter as cooler air. In the evaporation mode, the bypass damper 122 canbe closed.

In an economizer mode, the bypass damper 122 can be open and thescavenger air inlet 110 can be closed. With the bypass damper 122 open,the scavenger air can enter the top level 106 downstream of the DEC 104and bypass the DEC 104. This can result in a reduction of the pressuredrop of the scavenger air through the top level 106 that is caused atleast in part by the DEC 104. The system 100 can operate in theeconomizer mode if the outdoor (scavenger) air is at a temperature lowenough to indirectly cool the data center process air to the target orset point temperature without the scavenger air passing through the DEC104. In one example, determination of the operating mode can be based onthe supply air at the process air outlet 116 and comparison of ameasured process air outlet temperature 116 with a target or set pointtemperature for the supply air.

It is recognized that it can be desirable to hold the temperature of theprocess supply air at or near a supply air temperature set point orrange. For example, it may be common to set the target supply airtemperature at approximately 75 degree Fahrenheit. However, the setpoint can be changed during operation of the system 100. In one example,if the outdoor air conditions are hot, the set point may be increased ora range may be provided. This can allow the system to run in aneconomizer mode over a larger range of conditions.

In the economizer mode, the scavenger air enters the top level 106through the bypass damper 122 and passes through the sensible wheel 102to indirectly cool the process air, as described above. In one example,the bypass damper 122 for the DEC 104 is located in the top level 106 atsuch a position that essentially 100% of the scavenger air bypasses theDEC 104, even though the bypass damper 122 is shown in FIG. 1 as beingin line with the DEC 104. (This applies to the bypass dampers for theDEC of other systems shown in later figures and described herein—the DECbypass damper can allow for all of the scavenger air to bypass the DECby locating the bypass damper downstream of the DEC and closing thescavenger air inlet 110.)

The scavenger air exits the top level 106 at the scavenger air outlet112 at a higher temperature, relative to its temperature when enteringthrough the bypass damper 122. In the economizer mode, the process airpasses through the bottom level 108 as described above for theevaporation mode—hot process air enters the unit from the process airinlet 114, passes through the wheel 102 and is indirectly cooled to alower temperature. The process air exiting the bottom level 108 at theoutlet 116 is thus at a lower temperature relative to at the inlet 114.

In some examples, the system of FIG. 1 is a 100% recirculation systemfor the data center air, or air from another enclosed space. The hotdata center air enters the system 100 at the process inlet 114 andpasses through the filter 124, the sensible wheel 102, and the fan 126.The data center or process air is conditioned (indirectly cooled) usingthe scavenger air. The data center or process air then exits the system100 at the process outlet 116 as cold aisle supply air. Essentially allof the hot aisle return air that enters the bottom level 106 is returnedto the data center, or other enclosed space, as cold aisle supply air.It is recognized that some process air may be lost, for example, toleakage in the sensible wheel 102.

The process and scavenger air streams pass through the system 100 inseparate flow paths. The flow path of the process air stream is throughthe bottom level 108 and the flow path of the scavenger air stream isthrough the top level 106. The system 100 can include a partitionseparating the top 106 and bottom 108 levels. As such, the flow paths donot mix with each other. The sensible wheel 102 can span, or be disposedat least partially in, both the top 106 and bottom 108 levels. Althoughthe flow path of the scavenger air and the flow path of the process aircan remain separate from one another, it is recognized that a minimalamount of process air or a minimal amount of scavenger air can be lostto the sensible wheel 102 or other AAHX used in place of the sensiblewheel 102. It is the scavenger air stream that conditions the processair stream by first passing through the DEC 104 and then indirectlycooling the process air stream in the wheel 102.

As described above, in some examples, a determination of the operatingmode of the system 100 can be based in part, on a set point temperaturefor the process air at the outlet 116. In some examples, the system 100can operate based on a process air outlet set point of 75 degreeFahrenheit. In other examples, it can be acceptable to operate thesystem 100 at a process air outlet range, such as for example, 75 to 78degree Fahrenheit. Thus the system 100 can operate in an economizer modeso long as the process air at the outlet 116, which is supplied back tothe enclosed space, is at a temperature below the upper limit, such as,78 degree Fahrenheit. If the system cannot operate in the economizermode and delivery an outlet temperature below 78 degree Fahrenheit, thesystem 100 can change to an evaporation mode. Additional cooling can beprovided from the DEC 104 in the evaporation mode to return the processair outlet temperature to an acceptable value or range. The wheel speedof the sensible wheel 102 and the flow rate of the scavenger air can bevaried and controlled as part of the operation of the system 100 to meetthe set point or range for the cold aisle supply air.

In some examples, the system 100 of FIG. 1 may exhibit the followingcharacteristics and/or operate according to the following parameters.This assumes the process air at the inlet 114 is at 102 degreeFahrenheit and the process air at the outlet 116 is at 75 degreeFahrenheit, the sensible wheel 102 has 78% sensible effectiveness andthe DEC 104 has 95% effectiveness. A temperature of the hot aisle returnair (the process air at the inlet 114) may include about a 1-2 degreeFahrenheit temperature increase due to the presence of fans in thesystem 100 and heat from the fans caused by electrical energy to drivefans. The economizer mode can be employed if the outside air dry bulb(OADB) temperature is less than or equal to approximately 67 degreeFahrenheit. In this mode, a wheel speed of the sensible wheel 102 and aflow rate of the scavenger air through the top level 106 can be variedand controlled. The evaporation mode can be employed if the OADBtemperature is greater than 67 degree Fahrenheit and the outside air wetbulb (OAWB) temperatures is less than or equal to 66 degree Fahrenheit.Similarly here, the wheel speed of the sensible wheel 102 and the flowrate of the scavenger air can be varied and controlled.

The above parameters are based on particular specifications for thecomponents in the system 100, including the DEC 104 and the wheel 102.It is recognized that the size or capacity of one or more components canbe changed, which can change the overall cooling capacity of the system100. As described above, the system 100 can be configured to operate ata target or set point temperature (or range having an upper and lowerlimit) for the process air at the outlet 116—typically the targettemperature stays the same during operation of the data center, orwhatever environment the process air is being returned to. However, theoutside conditions (temperature and humidity) of the scavenger air canvary significantly, and the load or activity of the data center can varysignificantly. Thus operation of the system 100 can account forvariations in the outside conditions and the activity inside the datacenter. The above control conditions are provided as examples fordetermining the operating mode of the system 100. Different thresholdsor set points can be used in other examples. Moreover, it is recognizedthat the thresholds and set points can also vary depending on otherfactors, such as, for example, the heat load on the system 100.

A similar system relative to the system 100 of FIG. 1 can be configuredas an end-on delivery system (mounted to a side wall of an enclosedspace) instead of a roof-top system. Such a system can be a side-by-sideunit with a sensible wheel and a DEC, in which the scavenger and processair streams can be side-by-side. Such side-by-side system can run inevaporation and economizer modes in a similar manner as described abovewith reference to the system 100 of FIG. 1. Additionally, suchside-by-side system can exhibit similar characteristics or operateaccording to similar parameters as those described above with referenceto the system 100 of FIG. 1.

FIG. 2 depicts an example roof-top system 200 and, similar to the system100, can include top 206 and bottom 208 levels, a sensible wheel 202 anda DEC 204. The system 200 can operate in an economizer mode and anevaporation mode, similar to FIG. 1. Scavenger or outside air can passthrough the top level 206 through a scavenger air inlet 210 and outlet212. Process air can pass through the bottom level 208 through a processair inlet 214 and outlet 216. As similarly described above in referenceto the system 100, the system 200 can include fans 220 and 226, as wellas filters 218 and 224. As described in the context of the system 100,the system 200 can also be employed in an end-on delivery application.

Compared to the system 100, the system 200 can include a directexpansion (DX) coil 240 (an air cooled condenser) and a condenser coil242 (described below). The DX coil 240 can provide additional cooling inthe process air stream and can facilitate operation of the system 200 ina third mode referred to as an evaporation plus DX mode or a DX mode.The DX coil 240 is shown in FIG. 2 in the bottom level 208 between thesensible wheel 202 and the fan 226; it is recognized that the DX coil240 can be located downstream of the fan 226.

Similar to the system 100, the scavenger air passes through the DEC 204and is evaporatively cooled to its wet-bulb temperature. The cooledscavenger air then passes through the sensible wheel 202 and indirectlycools the process air in the bottom level 208 through sensible cooling.The process air exiting the sensible wheel 202 passes through the DXcoil 240 for further cooling in the DX mode.

The DX mode can be used, for example, to meet a target temperature orset point for the process air exiting the outlet 216 when the cooling isnot sufficient using the DEC 204 and the sensible wheel 202 in anevaporation mode. As described above, in some examples, the targettemperature of the cold aisle supply air can be 75 degree Fahrenheit. Ifthe system 200 is not able to cool the process air to the targettemperature in the evaporation mode, even after making adjustments tothe components of the system 200 (such as operating speeds), the system200 can switch to the DX mode. Thus the selection of the mode can becontrolled through the target temperature, or acceptable range, for thesupply air. It is recognized that the target temperature or range can beadjusted by the user. In some examples, the operation of the system 200can be based in part on the OADB and OAWB temperatures. Exampletemperatures provided above for the system 100 for the economizer andevaporation modes can also be applicable for those two modes in thesystem 200. In some examples, the DX mode may be employed in the system200 if the OAWB temperature is greater than 66 degree Fahrenheit. Inthis mode, the sensible wheel 202 and the fan 220 may run at full speed.

The condenser coil 242 can be located in the top level 206 downstream ofthe sensible wheel 202 and the condenser coil 242 can be used in the DXmode. The scavenger air can pass through the condenser coil 242 to coolthe refrigerant from the DX coil 240 in the bottom level 208. Thecooling circuit for the DX coil 240 and the condenser coil 242 is notshown in FIG. 2, but an example of a similar cooling circuit is shown inFIG. 3. The scavenger air passing through the condenser coil 242 canreject heat from the refrigerant of the DX coil 240. The scavenger aircan be exhausted to outside, through the scavenger air outlet 212, aswarm and humid air. The cooled refrigerant exiting the condenser coil242 can flow back into the DX coil 240. In the DX mode, a compressorspeed (load) of a compressor (see FIG. 3) between the DX coil 240 andthe condenser 242 may be controlled.

Similar to the system 100 of FIG. 1, the system 200 can include a bypassdamper 222 that allows the scavenger air to enter the top level 206without passing through the DEC 204. The scavenger air bypasses the DEC204 in an economizer mode. The system 200 can also include a bypassdamper 244 in the bottom level 208, which causes the process air tobypass the DX coil 240, and a bypass damper 246 in the top level 206,which causes the scavenger air to bypass the condenser coil 242. In theDX mode, the bypass dampers 222, 244 and 246 are closed, and the airinlets 210 and 214 are open.

In the evaporation mode, the system 200 can operate similarly to thesystem 100 in that the bypass damper 222 can be closed. However, unlikethe system 100, the bypass dampers 244 and 246 can be open such that theprocess air in the bottom level 208 bypasses the DX coil 240 and thescavenger air in the top level 206 bypasses the condenser coil 242. Inthe economizer mode, the scavenger air inlet 210 can be closed and thescavenger air can enter the top level 206 through the bypass damper 222and then bypass the condenser coil 242 after passing through thesensible wheel 202; the process air can enter the bottom level 208 andpass through the sensible wheel 202 and then bypass the DX coil 240.

As described above in reference to FIG. 1, the bypass damper 222 for theDEC 204 can be installed in a location in the top level 206 such thatthe scavenger air enters the bypass damper 222 in such a way, forexample, downstream of the DEC 204, that the scavenger air essentiallycompletely bypasses the DEC 204 (and the scavenger air inlet 110 isclosed). In some examples, the bypass dampers 244 and 246 can beconfigured such that, when the bypass dampers 244 and 246 are open, theprocess air can physically still pass through the DX coil 240 and thescavenger air 242 can physically still pass through the condenser coil242. However, in operation, the process air and scavenger air will takethe flow path of less resistance and thus the majority of the air willpass through the dampers 244 and 246. It is recognized that some amountof air will pass through the DX coil 240 and the condenser coil 242. Thelower pressure drop caused by the bypass of the DX coil 240 and thecondenser coil 242 can increase an efficiency of the system 200.

Table 1 below lists a range of sensible effectiveness of the wheel 202and the impact the sensible effectiveness has on the OADB temperaturelimit and the OAWB temperature limit, as well as overall wet bulbeffectivess.

TABLE 1 Wheel sensible OADB limit for OAWB limit for Unit wet bulbeffectiveness economizer mode evaporation mode effectiveness (%) (° F.)*(° F.)* (%)* 70 63.5 61.8 67.3 72.5 64.8 63.2 69.7 75 66 64.5 72.1 77.567.2 65.8 74.5 80 68.3 66.9 77 82.5 69.3 67.9 79.3 85 70.2 68.9 81.7

The values in Table 1 assume a 95% effective evaporative cooler, coldaisle supply temperature target of 75° F., and hot aisle returntemperature of 102° F. (including a 2° F. temperature increase due tofans).

The unit wet bulb effectiveness shown in Table 1 represents an overalleffectiveness of the system 200 for cooling the process air stream downto a dry bulb temperature that is the same as the outdoor air wet bulb(OAWB) temperature. The calculation for unit wet bulb effectiveness isshown in Equation 1 below.

$\begin{matrix}{{{wet}\mspace{14mu} {bulb}\mspace{14mu} {effectiveness}} = {\frac{({mcp}){{process}\left( {{THotaisle} - {TColdaisle}} \right)}}{({mcp}){\min \left( {{THotaisle} - {TOAWB}} \right)}} \times 100}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, mcp is the product of the mass flow rate of air and thespecific heat of the air. In the numerator, mcp of the process air isused. In the denominator, the (mcp)min is the smaller of the mcp of theprocess air and the mcp of the scavenger air. In the numerator, the mcpof the process air is multiplied by the temperature difference betweenthe process air at the inlet 114 (THotaisle) and the process air at theoutlet 116 (TColdaisle). In the denominator, the mcp of either theprocess air or the scavenger air is multiplied by the temperaturedifference between the process air at the inlet 114 (THotaisle) and theoutdoor air wet bulb (OAWB).

A unit wet bulb effectiveness of 100% means that the dry bulbtemperature of the supply air (leaving the bottom level 200 at theoutlet 216) is equal to the outdoor air wet bulb (OAWB) temperature.This is not possible given that there will be some inefficiency in theequipment, such as the sensible wheel 202 or the DEC 204.

FIG. 3 depicts an example DX system 10 that can be included in aroof-top or end-on delivery system like the system 200 of FIG. 2. The DXsystem can be used in other roof-top or end-on delivery systemsdescribed herein. The system 200 of FIG. 2 included the DX coil 240 andthe condenser coil 242 but did not show the additional components of thecooling circuit of the DX system 10 which are included in FIG. 3. The DXsystem 10 can include a DX coil 40, similar to the DX coil 240, whichcan be located in a process air stream. In some cases, there may not becondensation on the DX coil 40. In some examples, a micro-channel DXcoil can be used in the system of FIG. 3.

The DX system 10 can also include a condenser 42, similar to thecondenser 242, which can be located in a scavenger air stream. Therefrigerant from the DX coil 40 can exit the DX coil 40 and flow througha compressor 48 and then through the condenser 42. The scavenger airpassing through the condenser 42 can cool the refrigerant. After exitingthe condenser 42, the refrigerant can flow through an expansion valve 50(for controlling the refrigerant) before flowing back to the DX coil 40.

When a system, like the system 200 of FIG. 2, uses the DX system 10, itis because additional cooling is needed or beneficial, beyond thecooling provided by a DEC and an AAHX, such as a sensible wheel. It isrecognized that the cooling capacity provided by the DX system 10 can bemodulated and change based on the needs of the DX system 10. It may notbe necessary to operate the DX system 10 at full capacity and theoperation can vary across a cooling range rather than operating the DXsystem 10 in only active or inactive modes.

FIG. 4 depicts an example direct evaporative cooler (DEC) 60 that can beincluded in a roof-top or end on delivery system and may be similar tothe DECs 104 and 204 in the systems 100 and 200, respectively, describedabove. The DEC 60 can also be used in the other roof-top or end ondelivery systems described herein. The DEC 60 can include an evaporationmedia 62, a mist eliminator 63, a water collection pan/tank 64, a watersprayer 65 and a water treatment unit 66. The scavenger air or outdoorair can pass through the evaporation media 62 which is wetted with waterfrom the sprayer 65. In some examples, the evaporation media can includefiberglass, but other materials can be used in the alternative or inaddition to fiberglass. As the air passes through the media 62, thewater evaporates into the air which results in cooling. The cooled aircan pass through the mist eliminator 63 to remove liquid droplets fromthe air. As described above, the cooled air exiting the DEC 60 can thenpass through a sensible wheel to reject heat from the process air.

Excess water from the evaporation media 62 can be collected in thecollection pan/tank 64 and then recirculated back to the water sprayer65. The water can pass through an optional water treatment unit 66located before the water sprayer 65. Make-up water can be supplied tothe collection pan/tank 64 and a purge can periodically be performed.

It is recognized that other types of direct evaporative coolers can beused in the roof-top and end-on delivery systems described and shownherein.

FIG. 5 depicts an example roof-top system 500 that is similar to thesystems 100 and 200 of FIGS. 1 and 2 and can include several of the samecomponents. The system 500 can also be employed in an end-on deliveryapplication. In addition to the components shown in the system 200 ofFIG. 2, the system 500 can include a liquid-to-liquid heat exchanger(LLHX) 552, or water cooled condenser, in a top level 506. A compressor548 is shown in the bottom level 508. The system 500 includes a DEC 504and a DX coil 540, similar to the system 200 of FIG. 2. The LLHX 552 canbe used to cool the DX refrigerant of the DX coil 540 using cool watersupplied from the DEC 504. The system 500 can include a bypass damper522 for bypassing the DEC 504 and a bypass damper 544 for bypassing theDX coil 540.

As with other disclosed examples, the system 500 of FIG. 5 can operatein multiple modes. In an economizer mode, the bypass dampers 522 and 544are open, the DEC 504 is disabled and the scavenger and process air flowis similar to that described for the economizer mode of the system 100of FIG. 1. The system 500 of FIG. 5 can also operate in an evaporationmode, in which the bypass damper 522 is closed, the bypass damper 544 isopen, and the scavenger and process air flow is similar to thatdescribed for the evaporation mode of the system 100 of FIG. 1. In a DXmode, the bypass dampers 522 and 544 are closed, the scavenger air flowsthrough the top level 506 from the scavenger air inlet 510 to the outlet512, and the process air flows through the bottom level 508 from theprocess air inlet 514 to the outlet 516.

The system 500 includes a water loop that can be used for additionalcooling. Water flows over the media of the DEC 504 (see FIG. 4) andevaporates to cool the scavenger air passing through the top level 506.Both the scavenger air and the water can be cooled to the OAWBtemperature. The cooled water, which can be collected in a collectionpan/water tank (not shown in FIG. 5, see FIG. 4), flows into the LLHX552 (water cooled condenser) and cools the refrigerant. (The water inthe collection pan can be the coldest water within the DEC 504.) Thecooled/condensed refrigerant flows from the LLHX 552, through anexpansion value 550 for refrigerant control, and into the DX coil 540 inthe bottom level 508 to reject heat from the process air flowing throughthe bottom level 508. After exiting the DX coil 540, the refrigerant canflow through a compressor 548 prior to returning to the LLHX 552.

After passing through the LLHX 552, the water can flow back to the DEC504. In one example, the water, which is now warm, can go directly backto the sprayer at the top of the DEC 504, rather than back to thecollection pan.

Although the LLHX 552 is shown in FIG. 5 as being downstream of the DEC504, the LLHX 552 does not have to be configured as shown. In someexamples, a water piping circuit can be located around or in proximityto the DEC 504 and the LLHX 552 can be within the circuit. In otherexamples, the LLHX 552 can be in the collection pan of the DEC 504, andthe warm water exiting the LLHX 552 can get pumped back to the sprayerat the top of the DEC 504.

In summary, in the system 500, the cold water in the DEC 504 can be usedto cool the refrigerant from the DX coil 540, using the LLHX 552. Thecooled refrigerant flows back to the DX coil 540 in the bottom level andcools the process air flowing through the DX coil 540 in the bottomlevel 508.

The system of FIG. 5 may provide a number of advantages. Water cooledcondensers, such as the LLHX 552 shown in FIG. 5, may be operated withimproved efficiency over air cooled condensers. The warm water comingfrom the LLHX 552 can function to boost the evaporation potential of theDEC 504. Additionally, the system 500 may have a reduced pressure dropon the scavenger air side (the top level 506), as compared to the system200 of FIG. 2, given the LLHX 552 and the elimination of an air cooledcondenser (such as the condenser coil 242 of FIG. 2).

FIG. 6 depicts an example system 600 for roof-top or end-on deliveryapplications. The system 600 can be similar to the system 500 andinclude many of the same components, including a DEC 604 and a wheel602. In contrast to the system 500, the system 600 can exclude a LLHX inthe top level 606. The system 600 can operate in the three modesdescribed above—an economizer mode, an evaporation mode, and a DX mode(evaporation plus DX). The system 600 can include a DX coil 670, whichcan be located in the DEC 604. A DX coil 640 (similar to DX coil 240 and540 of the systems 200 and 500, respectively) is shown in dotted linesin FIG. 6 and can optionally be included within the system 600. The DXcoil 640 is described in further detail below.

The DX coil 670 can cool water inside the water collection pan/watertank (not shown in FIG. 6, see FIG. 4) of the DEC 604 below the outdoorair wet bulb temperature, when the system 600 is running in the DX mode.As described above, the DX mode can be used if cooling from the DEC 604and the sensible wheel 602 is not sufficient, based, for example, on aset point or range for the process supply air returned to the enclosedspace. Instead of having a DX coil in the process air stream of thebottom level 608 (as shown in FIGS. 2 and 5), the DX coil 670 can be inthe DEC 604 of the scavenger air stream.

As a result of the DX coil 670, the cold water in the DEC 604 can becooled down further and the DEC 604 can provide additional cooling foruse in indirectly cooling the process air in the sensible wheel 602.

As shown in FIG. 6, water exiting the DX coil 670 can flow to acompressor 648 in the process air stream and to a condenser coil 642 inthe scavenger air stream. The water can then flow through an expansionvalve 650 prior to returning to the DX coil 670 in the DEC 604. It isrecognized that the compressor 648 can be located within a differentlocation within the system 600. A particular location selected candepend, in part, on space availability or installation costs.

The cooling water loop or circuit in the system 600 can be the same asthe cooling water loop in the system 500, except that in the system 600,the water can flow through a condenser coil instead of the LLHX 552. Asize and shape of the water collection pan may be different toaccommodate the DX coil 670 in the DEC 604.

In some examples, the system 600 can remove the DX coil from the processairstream (as shown in FIGS. 2 and 5), and the process air streamflowing through the bottom unit 608 can have a reduced pressure dropwhich can increase the efficiency of the system 600. It is estimatedthat the process side pressure drop will decrease by 15% to 20% byremoving the DX coil from the bottom level 608.

As similarly shown in FIG. 2, the condenser coil 642 can be located inthe scavenger air steam. In another example, the condenser coil can be aseparate module located outside of the scavenger air flow path. In oneexample, the condenser coil can be mounted external to the system 600.Removing the condenser coil 642 from the top level 606 can eliminate thepressure drop of the condenser coil when the system 600 is running inthe economizer and evaporator modes and not using a DX coil. A condensercoil module separate from the system 600 may add additional costs andtake up extra space.

In the event of a water outage or reduction, the DEC 604 and the DX coil670 could be out of order or limited significantly. As such, the coolingpotential from both the DEC 604 and the DX coil 607 could be eliminatedor compromised. In one example, the system 600 can include the DX coil640 in the bottom level 608, which can be present in addition to the DXcoil 670 in the DEC 604. The DX coil 640 can be used to reject some ofthe heat from the process air stream, if there was a water failure thatdiscontinued or significantly limited use of the DEC 604 and the DX coil670. Thus the DX coil 640 can act as a back-up to the DEC 604 and the DXcoil 670. In one example, both the DX coil 670 and the DX coil 640 canbe used simultaneously during operation of the system 600. One or bothof the DX coils 640 and 670 can have an overall smaller size andcapacity. Both DX coils 640 and 670 can be used simultaneously, forexample, at a peak cooling load.

FIG. 7 depicts an example system 700 for roof-top or end-on deliveryapplications and can be similar to the system 200 of FIG. 2 and includemany of the same components, including a DEC 704 and a wheel 702. Thesystem 700 can operate in the three modes described above. In contrastto the system 200, the system 700 can include a pre-cooling coil772upstream of the DEC 704 in the top level 706.

The precooling coil 772 may function to depress the outdoor air wet-bulb(OAWB) temperature when the scavenger or outdoor air entering the topunit 706 through the scavenger air inlet 710 is hot and humid and permitthe system 700 to cover substantially all of the load of the data center(or other enclosed space the system 700 is providing cooling to) withevaporative cooling at higher OAWB temperatures. In other words, raisingthe OAWB limit permits the system 700 to operate in the evaporationmode, without DX cooling, across a wider range of conditions. The system700 can increase the evaporation potential in the DEC 704.

The system 700 may be run in an economizer mode similar to thatdescribed above with reference to FIG. 2 with the bypass dampers 722,744 and 746 open and the air inlets 708 and 710 closed. In theeconomizer mode, the scavenger air bypasses the pre-cooling coil 772,the DEC 704 and the condenser coil 742, and the process air bypasses theDX coil 740.

The system 700 may be run in an evaporation mode and a DX mode(evaporation plus DX mode). In those modes, the outdoor air (scavengerair) enters the top level 706 through the scavenger air inlet 710 andpasses through the pre-cooling coil 772 which can sensibly cool theoutdoor air and depress its wet bulb temperature; the scavenger air canthen pass through the DEC 704 which can cool the scavenger air to itswet bulb temperature (the scavenger air new wet bulb temperature is nowdifferent (lower) than the outdoor air wet bulb temperature). Thescavenger air can next pass through the sensible wheel 702 andindirectly cool the data center air.

In the evaporation mode, the bypass damper 722 can be closed and theother bypass dampers 744 and 746 can be open. As such, the scavenger airbypasses the condenser coil 742 in the top level 706 and the process airbypasses the DX coil 740 in the bottom level 708.

In the evaporation plus DX mode, the bypass dampers 722, 744, and 746can all be closed. As such, the scavenger air passes through thecondenser coil 742 and the process air passes through the DX coil 740for additional cooling. Determining which mode the system operates incan be based on similar parameters and conditions as described above inreference to the systems 100 and 200 of FIGS. 1 and 2.

With reference to the water loop included in the system 700 between theDEC 704 and the pre-cooling coil 772, the water in the collectionpan/tank (not shown in FIG. 7, see FIG. 4) of the DEC 704 can flow intothe pre-cooling coil 772 and collect heat from the scavenger air passingthrough the pre-cooling coil 772. The warm water can be returned to thecollection pan/tank. The water can be sprayed on the evaporation mediaas described above in reference to FIG. 4 and evaporate. The evaporationprocess can cool the scavenger air to its wet bulb temperature.

FIG. 8 depicts an example system 800 for roof-top or end-on deliveryapplications and can be similar to the system 700 of FIG. 7. The system800 can operate in the three modes described above. In contrast to thesystem 700, the system 800 can include a cooling coil 880 in the bottomlevel 808 between the sensible wheel 802 and the DX coil 840, and abypass damper 882 in the top level 806 configured to allow the scavengerair to bypass the pre-cooling coil 872. As shown in FIG. 8, the fan 820can be located downstream of the condenser coil 842, which is oppositeto the configuration in the system 700. It is recognized that any of thesystems described herein and shown in the figures could have the fan andcondenser coil in either order in the scavenger air flow path. In someexamples, the condenser coil 642 can alternatively be located upstreamof the fan 620 such that the condenser coil 642 does not have to dealwith the added heat from the electrical energy of the fan 620.

The cooling coil 880 may function to cool the process air after thesensible wheel 802 using the cold water in the DEC 804. This canincrease the evaporation potential in the DEC 804 since a temperatureincrease of the water, from the cooling coil 880, can boost theevaporation in the DEC 804. The pre-cooling coil 872 can providepre-cooling or pre-heating. In hot and humid climates, the pre-coolingcool 872 can function to depress the outdoor air wet bulb temperatureand increase the evaporation potential in the DEC 804. In moderateoutdoor air temperatures with relatively high humidity, the pre-coolingcoil 872 can heat the outdoor air entering the inlet 810 to increase theevaporation potential in the DEC 804.

The economizer mode of the system 800 can be substantially similar tothe economizer mode described with reference to the systems 100 and 200.

In the evaporation mode, the DX and condenser bypass dampers 844 and 846can be open and the other bypass dampers 822 and 882 can be closed.However, the pre-cooling coil 872 can be bypassed, using bypass damper882, in hot and humid conditions when the OADB temperature is lower thanthe water temperature entering the pre-cooling coil 872. Operation withregard to the scavenger air in the top level 806 may be substantiallysimilar to the system 700 of FIG. 7. Operation with regard to theprocess air in the bottom level 808 may be substantially similar to thesystem 700, except that the process air can also pass through thecooling coil 880. Additionally, the cooling coil 800 may provide extracooling to the process air, reduced the cooling needed from the DX coil840, and increase the evaporation potential in the DEC 804.

In the DX mode (evaporation plus DX), all of the bypass dampers 822,842, 846 and 882 can be closed. However, the pre-cooling coil 872 can bebypassed, using bypass damper 882, in hot and humid conditions when theOADB temperature is lower than the water temperature entering thepre-cooling coil 872. Operation with regard to the scavenger air in theDX mode may be substantially similar to the system 700. Operation withregard to the process air in the DX mode may be substantially similar tothe system 700, except that the process air will be cooled in threestages (sensibly): the sensible wheel 802, the cooling coil 880, and theDX coil 840.

The system 800 can include a water loop that facilitates operation ofthe system 800 as described above. The water from the DEC 804 can flowthrough an expansion valve 884 and through the cooling coil 880. Thewater can then pass into a diverter valve 886, which can direct thewater either back to the DEC 804 or to the pre-cooling coil 872. If thewater is directed to the pre-cooling coil 872, the water exiting thepre-cooling coil 872 can then flow back to the DEC 804.

In the economizer mode, the water loop may be closed since the DEC 804and the cooling coil 880 are not being utilized. The water loop may beactive in the evaporation and DX modes. In some cases, when active, thewater is sprayed on the DEC media (see FIG. 4) in the DEC 804 and thewater is cooled to the wet bulb temperature of the scavenger air passingthrough the DEC 804. The cold water then passes through the cooling coil880 in the bottom level 808 to further cool the process air exiting thesensible wheel 802. As a result, the temperature of the water increases.If the temperature of the water at the outlet of the cooling coil 880 ishigher than the OADB temperature in hot and humid climates, then thewater flows to the water collection pan/tank in the DEC 804 and bypassesthe pre-cooling coil 872 through the use of diverter valve 886.Otherwise, the water flows from the cooling coil 880 to the pre-coolingcoil 872 to depress the OAWB temperature. The pre-cooling coil 872causes the temperature of the water to increase again. The water flowsback into the collection pan/tank of the DEC 804 and the cyclecontinues. The pre-cooling coil 872 acts as a preheating coil inmoderate climates to heat the outdoor air and increase the evaporationpotential in the DEC 804.

FIGS. 9A and 9B depict an example end-on delivery system 900 including ahorizontally mounted sensible wheel 903 and a DEC 905. FIG. 9A is an endview of the system 900 and shows a scavenger air side of the system 900.The opposite end of the system 900 (not shown) is a process air side.FIG. 9B is a side view of the system 900 and shows the scavenger andprocess air flowing in generally opposite directions relative to oneanother. As described above in reference to the roof-top deliverysystems, in an example, the process air can come from a data center inthe form of hot aisle return air and then be returned to the data centeras cold aisle supply air.

As similarly described above in reference to the roof-top deliverysystems, the system 900 can include a partition separating the scavengerair side of the system 900 from the process air side of the system 900.As such, the scavenger air flow path and the process air flow path canremain separate from one another in the system 900. The sensible wheel903 can span or be disposed in both the scavenger air side and theprocess air side.

The system 900 of FIGS. 9A and 9B may allow for a more compact unit thanone including a vertically mounted sensible wheel. An air cooledcondenser, such as condenser coil 243, can be used in the system 900.The system 900 can include the three modes described above—economizer,evaporation, and evaporation plus DX. Operation of the system 900 forall operating modes can be substantially similar to those describedabove with reference to the system 200 of FIG. 2. It is recognized thatan end-on delivery system similar to the system 900 could be modified toinclude additional components shown and described above for roof-topsystems, such as for example, fans, filters, liquid-to-liquid heatexchangers, a DEC with a DX coil located therein, pre-cooling coils,etc.

FIGS. 10-12 depict an example of a roof-top system 1000, which cansimilarly be employed in an end-on delivery application. The system 1000may operate in a manner substantially similar to the system 200 of FIG.2. However, the system 1000 as shown in FIGS. 10-12 provides additionaldetail, as compared to FIG. 2, with respect to arrangement, number, andconfiguration of different components of the example system. It isrecognized that other roof-top and end-on delivery systems are includedwithin the scope of the present application despite having differentarrangements of components and different numbers of components, ascompared to the system as specifically shown in FIGS. 10-12 and theother systems shown and described herein.

FIG. 10 is a side view of the system 1000 including a top level 1006 anda bottom level 1008. Outside area (O/A) or scavenger air enters the toplevel 1006 through a scavenger air inlet 1010, passes through a filter1018, and through a DEC 1004. The scavenger air then passes through asensible wheel 1002 and then a fan 1020 is located upstream of acondenser coil 1042. After passing through the condenser coil 1042, thescavenger air returns to the outside as exhaust air (E/A). In aneconomizer mode, the air inlet 1010 is closed and the scavenger airenters the top level 1006 through bypass damper 1022 and passes througha filter 1023, and then flows through the sensible wheel 1002.

Return air (R/A) or process air, from a data center or other enclosedspace, enters the bottom level 1008 through a process air inlet 1014,passes through the sensible wheel 1002 and then passes through a DX coil1040. A fan 1026 is located upstream of the DX coil 1040. The processair then exits the bottom level 1008 through a process air outlet 1016as supply air (S/A). Also shown in the bottom level 1008 are one or morecompressors 1048 and a control box 1009.

FIG. 11 is a bottom view of the system 1000 of FIG. 10 and illustratesthe various components in the bottom level 1008. In one example, twocompressors 1048 are shown in the bottom level 1008, although it isrecognized that more or less compressors can be used. In one example,three fans 1026 are shown in the bottom level 1008, although it isrecognized that more or less fans can be used. FIG. 11 illustratesvarious access doors 1007 on the bottom level 1008. A filter for thereturn air (process air entering the bottom level 1008 at the inlet1014), although not shown in FIGS. 10 and 11, can be included in thesystem 1000, as shown in earlier figures—for example, the filter 124 inFIG. 1. Such filter for the return air can be similar to the filter 1018in the top level 1006.

FIG. 12 is a top view of the system 1000 and illustrates the variouscomponents in the top level 1006. The bypass dampers 1022 and filters1023 are better shown in FIG. 12 and allow the scavenger air to enterthe top level 1006 downstream of the DEC 1004 and bypass the DEC 1004 inan economizer mode. In one example, the system 1000 is configured tomeasure OADB temperature and the outside or scavenger air bypasses theDEC 1004 when the OADB temperature drops to and/or below an OADBtemperature limit. In such cases, the outside air is cool enough thatevaporative cooling is not needed to meet the load on the system 1000and bypassing the DEC 1004 can increase efficiency, reduce powerconsumption, and/or increase the longevity of the DEC 1004.

In one example, three fans 1020 are shown in FIG. 12 in the top level1006, although it is recognized that more or less fans can be used. FIG.12 illustrates various access doors 1007 on the top level 1006.

The system 1000 can operate similar to the system 200 of FIG. 2 and caninclude the various operating modes similar to the system 200. As such,in some examples, the system 1000 can include a bypass for the condensercoil 1042 and a bypass for the DX coil 1040. Although the condenser coilbypass and DX coil bypass are not shown in FIGS. 10-12, it is recognizedthat the system 1000 could include bypass dampers in the lower level1008 above the DX coil 1040 or in the upper level 1006 above thecondenser coil 1042. (See, for example, the bypass dampers 244 and 246in FIG. 2 for the system 200.)

The foregoing examples include a cooling system that combines a DEC andsensible wheel to cool the air in an enclosed space, such as, forexample, a data center. However, in other examples, different kinds ofAAHXs, such as, but not limited to, Glycol Run-around loops, heat pipes,or cross-flow AAHX, can be used with a DEC to indirectly cool the airfor the data center (or other enclosed space).

A system or unit configuration using a Glycol run-around loop and heatpipe along with a DEC can be similar to the example system 100 ofFIG. 1. In such an example, a Glycol run-around loop or heat pipe may beused instead of a sensible wheel to reject heat from the process airstream to the scavenger airstream. With a Glycol run-around loop, theprocess and scavenger air ducts do not need to be side-by-side, whichmay be one advantage of using a Glycol run-around loop in this system.Other configurations for the process and scavenger air streams as shownin other figures, such as for example the systems of FIGS. 2 and 5-8,are possible by using a Glycol run-around loop or a heat pipe whichmight end up with a more compact unit design in comparison with a unitusing a sensible wheel.

In terms of performance, a cooling system or unit with a sensible wheelmay deliver improved performance because the sensible wheel can have oneof the highest sensible performances, relative to other types of AAHXs.The AAHX sensible performance directly affects the overall systemperformance (i.e., wet-bulb effectiveness).

FIG. 13 depicts the effect of an AAHX on overall system performance orunit wet bulb effectiveness, as provided above as Equation 1 inreference to values shown in Table 1. FIG. 14 depicts the effect of anAAHX on the system outdoor air wet-bulb limit to reject 100% of the heatfrom an enclosed space, such as a data center, using only evaporation.The conditions used in the example presented in the graphs of FIGS. 13and 14 are as follows: Hot aisle return air: 100° F. dry bulb/50° F. dewpoint; Outdoor air conditions: 95° F. dry bulb/60° F. wet bulb; Processand scavenger air flow rates: 11,000 cubic feet per minute; DECeffectiveness used in the unit: 95%; and Range of study for the AAHAsensible effectiveness: 40% to 90%.

As indicated by the graphs of FIGS. 13 and 14, in some examples, onetype of AAHX, a counter-flow AAHX, may enable improved systemperformance in combination with a DEC in the scavenger air stream—thisis compared to other types of AAHX, including a sensible wheel or heatwheel.

FIGS. 15 and 16 depict two example systems including a DEC in thescavenger air stream in combination with a counter-flow flat-plate AAHXthat can be used to cool the air in an enclosed space like a datacenter.

FIG. 15 depicts an example roof-top delivery system 1500, although it isrecognized that the system 1500 can be modified for end-on deliveryapplications. The system 1500 can run in the three modes describedabove—economizer, evaporation, and DX (evaporation plus DX). The system1500 can include a top level 1506 that receives outdoor or scavenger airthrough a scavenger air inlet 1510 and a bottom level 1508 that receivesprocess or hot aisle return air through a process air inlet 1514. (Thedirection of the scavenger air stream is from left to right and theprocess air stream is from right to left. This is opposite to thedirection of the roof-top delivery systems shown in FIGS. 1-2, 5-8 and10-12. It is recognized that either arrangement for any of the roof-topdelivery systems can be used.)

The system 1500 is similar to the system 200 of FIG. 2 in that the toplevel 1506 includes a filter 1508, a DEC 1504, a fan 1520 and acondenser coil 1542, and the bottom level 1508 includes a DX coil 1540and a fan 1526. Although a filter is not shown in the bottom level 1508in FIG. 15, it is recognized that the system 1500 can include a filteras similarly shown in FIG. 2 for the system 200.

Instead of a sensible wheel, the system 1500 can include a counter-flowflat-plate AAHX 1590 that can use the scavenger air exiting the DEC 1504to cool or reject heat from the process air in the bottom level 1508. Asshown in FIG. 15, in one example, the system 1500 can operate with theAAHX 1590 as a counter-flow flat plate exchanger with counter parallelflow since the scavenger air and the process air flow in oppositedirections, but remain parallel to one another.

As described above in the example systems including a sensible wheel,the top 1506 and bottom 1508 levels of the system 1500 can be separatedfrom each other using a partition or other structure. As such, thescavenger air and the process air can remain separate as each flowsthrough the system 1500. As also described in reference to the sensiblewheel, the AAHX 1590 can span, or be at least partially disposed in,both the top 1506 and bottom 1508 levels.

As described above in reference to the system having a sensible wheel incombination with a DEC, and potentially other components, the system1500, as well as the system 1600, is a 100% recirculation system for theprocess air entering the system 1500. Moreover, as also described above,the process air and the scavenger air remain essentially separate fromone another and do not intermix in the systems 1500 and 1600, with theexception of air leakage in, for example, the AAHX.

The system 1500 can include dampers 1522, 1544 and 1546 which canfacilitate operation of the three modes described above in a similarmanner as described above for the system 200.

Although only the DX coil 1640 and the condenser coil 1642 are includedin FIG. 15 (and similarly in FIG. 16), it is recognized that the DX 1640and condenser 1642 coils are part of a DX system as similarly describedabove in FIG. 3.

FIG. 16 depicts an example roof-top delivery system 1600, which can bemodified for end-on delivery applications. The system 1600 can besimilar to the system 1500 and include a counter-flow flat-plate AAHX1690, as well as the other components described above in reference tothe system 1500. However, the counter-flow flat-plate AAHX 1690 canoperate with counter cross flow—the scavenger air and the process airflow in opposite directions and actually cross paths in the AAHX 1690.

In one example, the system 1600 can be a two level unit, as shown inFIG. 16, having a top level 1606 and a bottom level 1068. However, incontrast to the system 1500, both the scavenger air and the process airenter the top level 1606 at a scavenger air inlet 1610 and a process airinlet 1614, respectively. The inlets 1610 and 1614 are located generallyat opposite ends of the top level 1606. The scavenger and process airflows cross paths in the AAHX 1690 and the scavenger air exits the AAHX1690 in the bottom level 1608. The scavenger air exits the system 1600at a scavenger air outlet 1612 located at an opposite end relative tothe inlet 1610. The process air exits the AAHX 1690 in the bottom level1608 and exits the system 1600 at a process air outlet 1616 at anopposite end relative to the inlet 1614. The process air outlet 1616 isat an opposite end of the bottom level 1608 relative to the scavengerair outlet 1612. Both air streams flow from left to right, or right toleft, across a length of the system 1600.

As shown in FIG. 16, the fan 1620 can be located in the scavenger airflow path after the condenser coil 1642, which is opposite from theconfiguration in FIG. 15. (See the fan 1520 located before the condensercoil 1520.) As described above in the context of the systems using asensible wheel, the fan and condenser coil can be arranged in variousconfigurations.

It is recognized that systems similar to the systems 1500 and 1600,which include a counter-flow flat plate AAHX, instead of a sensiblewheel, in combination with a DEC, can also include additional componentsand features of the systems described above in FIGS. 3-12. As anexample, a cooling system similar to the system 600 of FIG. 6 couldinclude a counter-flow flat plate AAHX instead of the sensible wheel602, but include essentially the same additional components, including aDX coil located in the DEC.

In addition to potential performance benefits, counter-flow AAHXsystems, in accordance with the examples described herein, can provide asimilar reduction in overall system size, like a sensible wheel, ascompared to systems including other AAHXs. Moreover, counter-flow AAHXsystem may also reduce system costs relative to systems including otherAAHXs, including systems having a sensible wheel.

Although the examples of FIGS. 1, 2, 5-8, and 10-12 depict an optionalfilter upstream in the direction of air flow from an AAHX (e.g.,sensible wheel or counter-flow flat-plate), in other examples the filtercould be arranged downstream from the AAHX. Additionally, in the exampleof FIG. 2, the condenser coil 242 is arranged downstream of the fan 220on the scavenger air side of the system 200. However, in anotherexample, the condenser coil 242 can be arranged upstream of the fan 220on the scavenger air side of the system.

The examples of FIGS. 2, 5-8, 10-12, 15 and 16 include a DX coolingsystem with a fan downstream of the AAHX (e.g., the sensible wheel inFIGS. 2, 5-8 and 10-12, and a counter-flow flat-plate HX in FIGS. 15 and16) in the process air flow path, which is sometimes referred to as a“draw through” configuration. However, in other examples in accordancewith this disclosure, a fan could be arranged upstream of the AAHX inthe process air flow path, which is sometimes referred to as a “blowthrough” configuration.

The present disclosure includes methods of operating a cooling system tocontrol temperature in an enclosed space, such as, for example, a datacenter. Methods can include directing a scavenger air stream and aprocess air stream through a cooling system having an AAHX and a DEC asshown and described herein. The cooling system can include variouscombinations of the components and features described above. The methodscan include determining an operating mode of the cooling system based onone or more parameters, such as, for example, the outdoor airconditions. The method can include adjusting the cooling system, such asopening and closing inlets and dampers, based on the operating mode.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

All publications, patents, and patent documents referred to in thisdocument are incorporated by reference herein in their entirety, asthough individually incorporated by reference. In the event ofinconsistent usages between this document and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, or process that includes elements in addition to those listedafter such a term in a claim are still deemed to fall within the scopeof that claim. Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, the code can be tangibly stored on one ormore volatile or non-volatile tangible computer-readable media, such asduring execution or at other times. Examples of these tangiblecomputer-readable media can include, but are not limited to, hard disks,removable magnetic disks, removable optical disks (e.g., compact disksand digital video disks), magnetic cassettes, memory cards or sticks,random access memories (RAMs), read only memories (ROMs), and the like.

Examples, as described herein, may include, or may operate on, logic ora number of components, modules, or mechanisms. Modules may be hardware,software, or firmware communicatively coupled to one or more processorsin order to carry out the operations described herein. Modules mayhardware modules, and as such modules may be considered tangibleentities capable of performing specified operations and may beconfigured or arranged in a certain manner. In an example, circuits maybe arranged (e.g., internally or with respect to external entities suchas other circuits) in a specified manner as a module. In an example, thewhole or part of one or more computer systems (e.g., a standalone,client or server computer system) or one or more hardware processors maybe configured by firmware or software (e.g., instructions, anapplication portion, or an application) as a module that operates toperform specified operations. In an example, the software may reside ona machine-readable medium. In an example, the software, when executed bythe underlying hardware of the module, causes the hardware to performthe specified operations. Accordingly, the term hardware module isunderstood to encompass a tangible entity, be that an entity that isphysically constructed, specifically configured (e.g., hardwired), ortemporarily (e.g., transitorily) configured (e.g., programmed) tooperate in a specified manner or to perform part or all of any operationdescribed herein. Considering examples in which modules are temporarilyconfigured, each of the modules need not be instantiated at any onemoment in time. For example, where the modules comprise ageneral-purpose hardware processor configured using software; thegeneral-purpose hardware processor may be configured as respectivedifferent modules at different times. Software may accordingly configurea hardware processor, for example, to constitute a particular module atone instance of time and to constitute a different module at a differentinstance of time. Modules may also be software or firmware modules,which operate to perform the methodologies described herein.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. Also, in the above DetailedDescription, various features may be grouped together to streamline thedisclosure. This should not be interpreted as intending that anunclaimed disclosed feature is essential to any claim. Rather, inventivesubject matter may lie in less than all features of a particulardisclosed embodiment. Thus, the following claims are hereby incorporatedinto the Detailed Description, with each claim standing on its own as aseparate embodiment, and it is contemplated that such embodiments can becombined with each other in various combinations or permutations. Thescope of the invention should be determined with reference to entitled.

The present application provides for the following exemplary embodimentsor examples, the numbering of which is not to be construed asdesignating levels of importance:

Example 1 provides a system for controlling temperature in an enclosedspace and can comprise an air-to-air heat exchanger (AAHX) arranged in aflow path of process air between a process air inlet and outlet and in aflow path of scavenger air between a scavenger air inlet and outlet, anda direct evaporative cooler (DEC) arranged in the flow path of thescavenger air between the AAHX and the scavenger air inlet. The AAHX caninclude at least one of a counter-flow flat-plate heat exchanger and asensible wheel.

Example 2 provides the system of Example 1 optionally further comprisinga direct expansion (DX) system to provide additional cooling to theprocess air exiting the AAHX.

Example 3 provides the system of Example 2 optionally configured suchthat the DX system comprises a DX coil arranged in the flow path of theprocess air between the AAHX and the process air outlet, and a condensercoil arranged in the scavenger air flow path between the AAHX and thescavenger air outlet.

Example 4 provides the system of Example 2 optionally configured suchthat the DX system comprises a DX coil arranged in the flow path of theprocess air between the AAHX and the process air outlet and aliquid-to-liquid heat exchanger arranged in the scavenger air flow pathbetween the scavenger air inlet and the AAHX.

Example 5 provides the system of Example 4 optionally configured suchthat water from the DEC flows through the liquid-to-liquid heatexchanger and conditions refrigerant flowing from the DX coil throughthe liquid-to-liquid heat exchanger.

Example 6 provides the system of Example 2 optionally configured suchthat the DX system comprises a DX coil located in a collection tank ofthe DEC and configured to cool water in the collection tank.

Example 7 provides the system of Example 6 optionally further comprisinga second DX coil arranged in the process air flow path between the AAHXand the process air outlet.

Example 8 provides the system of any of Examples 1-7 optionally furthercomprising a pre-cooling coil arranged in the scavenger air flow pathbetween the scavenger air inlet and the AAHX.

Example 9 provides the system of Example 8 optionally further comprisinga cooling coil arranged in the process air flow path between the AAHXand the process air outlet, wherein water from the DEC flows through thecooling coil, the water flows back to the DEC or through the pre-coolingcoil and then the DEC, depending on conditions of the scavenger air atthe scavenger air inlet.

Example 10 provides the system of Example 9 optionally furthercomprising a DX coil arranged in the process air flow path between thecooling coil and the process air outlet.

Example 11 provides the system of any of Examples 1-10 optionallyconfigured such that the flow path of the scavenger air is through a topportion of the system and the flow path of the process air is through abottom portion of the system, and the system is configured for use on aroof top of a building containing the enclosed space.

Example 12 provides the system of Example 10 optionally furthercomprising a partition separating the top and bottom portions of thesystem, and wherein the flow path of the scavenger air and the flow pathof the process air remain separate from one another in the system.

Example 13 provides the system of Example 12 optionally configured suchthat the AAHX is disposed in both the top and bottom portions of thesystem.

Example 14 provides the system of any of Examples 1-10 optionallyconfigured such that the system is an end-on delivery system configuredfor attachment to a side of a building containing the enclosed space,and the flow path of the scavenger air is through a first side portionof the system and the flow path of the process air is through a secondside portion of the system such that the flow paths remain separate fromone another in the system.

Example 15 provides the system of Example 14 optionally furthercomprising a partition separating the first and second sides of theunit, and the AAHX is disposed in both the first and second sideportions.

Example 16 provides the system of any of Examples 1-15 optionallyconfigured such that the enclosed space is a data center.

Example 17 provides the system of any of Examples 1-16 optionallyconfigured such that the AAHX is a counter-flow flat plate heatexchanger configured for counter-parallel flow such that the flow pathof the scavenger air is in an opposite direction of the flow path of theprocess air.

Example 18 provides the system of any of Examples 1-16 optionallyconfigured such that the AAHX is a counter-flow flat plate heatexchanger configured for counter-cross flow such that the flow path ofthe scavenger air crosses the flow path of the process air inside theAAHX.

Example 19 provides a system for controlling a temperature in anenclosed space. The system can include a sensible wheel arranged in afirst flow path of process air between a process air inlet and outletand in a second flow path of scavenger air between a scavenger air inletand outlet, and a direct evaporative cooler arranged in the second flowpath upstream of the sensible wheel. The system can also include abypass configured to direct the scavenger air into the second flow pathat a location downstream of the DEC and upstream of the sensible wheel.

Example 20 provides the system of Example 19 optionally configured suchthat the bypass is a damper and the scavenger air inlet is closed whenthe damper is open.

Example 21 provides the system of Example 20 optionally configured suchthat the damper is open when the system is run in an economizer modesuch that the sensible wheel sufficiently conditions the process airwithout the direct evaporative cooler.

Example 22 provides the system of Example 21 optionally configured suchthat the damper is closed and the scavenger air inlet is open in anevaporation mode.

Example 23 provides the system of any of Examples 19-22 optionallyconfigured such that the process air comprises return air and supplyair, the return air being received from the enclosed space through theprocess air inlet and conditioned by the sensible wheel to produce thesupply air transmitted back into the enclosed space through the processair outlet.

Example 24 provides the system of any of Examples 19-23 optionallyconfigured such that the scavenger air comprises outside air andexhaust, the outside air being received from outside the enclosed spacethrough the scavenger air inlet and conditioned by the directevaporative cooler and the sensible wheel to produce the exhausttransmitted outside the enclosed space through the scavenger air outlet.

Example 25 provides the system of any of Examples 19-24 optionallyconfigured such that the first flow path is through a first portion ofthe system and the second flow path is through a second portion of thesystem, wherein the system further comprises a partition separating thefirst and second portions, and the first and second flow paths remainseparate from one another in the system.

Example 26 provides the system of Example 25 optionally configured suchthat the sensible wheel spans across both the first and second portionsof the system.

Example 27 provides the system of any of Examples 19-26 optionallyfurther comprising a direct expansion cooling device arranged in thefirst flow path between the sensible wheel and the process air outlet.

Example 28 provides the system of Example 27 optionally furthercomprising a condenser arranged in the second flow path between thesensible wheel and the scavenger air outlet, and configured to receive arefrigerant from the direct expansion cooling device such that thescavenger air conditions the refrigerant.

Example 29 provides the system of Example 28 optionally configured suchthat the condenser comprises at least one of an air cooled and a watercooled condenser.

Example 30 provides the system of any of Examples 27-29 optionallyconfigured such that the system is run in an evaporation-plus-DX mode inwhich the direct expansion cooling device provides cooling to theprocess air exiting the sensible wheel, and the evaporation-plus-DX modeoperates when the sensible wheel and the DEC cannot sufficientlycondition the process air without the direct expansion cooling device.

Example 31 provides the system of any of Examples 19-30 optionallyfurther comprising a cooling coil arranged in the first flow pathbetween the sensible wheel and the direct expansion cooling device.

Example 32 provides the system of any of Examples 19-31 optionallyfurther comprising a pre-cooling coil arranged in the second flow pathbetween the scavenger air inlet and the direct evaporative cooler.

Example 33 provides the system of any of Examples 19-32 optionallyfurther comprising a direct expansion cooling device in the DEC forconditioning water used in the DEC.

Example 34 provides the system of Example 33 optionally furthercomprising a direct expansion cooling device arranged in the first flowpath between the sensible wheel and the process air inlet and configuredas a back-up cooling system to the DEC.

Example 35 provides a system for controlling temperature in an enclosedspace. The system can include a sensible wheel arranged in a flow pathof process air between a process air inlet and outlet and in a flow pathof scavenger air between a scavenger air inlet and outlet, the scavengerair conditioning the process air using the sensible wheel, and a directevaporative cooler (DEC) arranged in the scavenger air flow pathupstream of the sensible wheel. The direct evaporative cooler cancondition the scavenger air prior to the scavenger air passing throughthe sensible wheel. The system can also include a direct expansioncooling device arranged in the process air flow path downstream of thesensible wheel for further conditioning the process air exiting thesensible wheel. The scavenger air flow path and process air flow pathcan be separate from one another in the system.

Example 36 provides the system of Example 35 optionally furthercomprising one or more bypass features that allow the system to run inan economizer mode and an evaporation mode, wherein the directevaporative cooler and the direct expansion cooling device are bypassedin the economizer mode, and the direct expansion cooling device isbypassed in the evaporation mode.

Example 37 provides the system of Example 36 optionally configured suchthat the one or more bypass features includes a DEC bypass damperlocated downstream of the direct evaporative cooler, and the DEC bypassdamper is open and the scavenger air inlet is closed in the economizermode.

Example 38 provides the system of any of Examples 35-37 optionallyfurther comprising a condenser located in the scavenger air flow pathand configured to condition a refrigerant exiting the direct expansioncooling device.

Example 39 provides the system of Example 38 optionally configured suchthat the one or more bypass features includes a DX bypass damper in theprocess air flow path and a condenser bypass damper in the scavenger airflow path, and wherein the DX bypass damper and the condenser bypassdamper are open in the economizer and evaporation modes, and the DXbypass damper and the condenser bypass damper are closed in anevaporation-plus-DX mode.

Example 40 provides the system of any of Examples 35-39 optionallyconfigured such that the system includes a set point temperature for theprocess air at the process air outlet, and an operating mode of thesystem is selected based on a comparison of a measured temperature atthe process air outlet to the set point temperature.

Example 41 provides the system of any one of Examples 35-39 optionallyconfigured such that the system includes a target temperature range forthe process air at the process air outlet, and an operating mode of thesystem is selected based on a comparison of a measured temperature atthe process air outlet to the target temperature range.

Example 42 provides a method of conditioning air in an enclosed space.The method can include passing scavenger air through a first portion ofa conditioning system, the scavenger air entering the first portion at ascavenger air inlet and exiting the first portion at a scavenger airoutlet, and passing process air through a second portion of theconditioning system, the process air entering the second portion at aprocess air inlet and exiting the second portion at a process airoutlet. The method can also include passing the scavenger air through adirect evaporative cooler (DEC) arranged in the first portion of theconditioning system to cool the scavenger air, and passing the cooledscavenger air and the process air through an air-to-air heat exchanger(AAHX) arranged in the conditioning system downstream of the directevaporative cooler. The cooled scavenger air can sensibly cool theprocess air in the AAHX. The AAHX can be arranged partially in the firstportion of the conditioning system and partially in the second portionof the conditioning system. The AAHX can include at least one of acounter-flow flat-plate heat exchanger and a sensible wheel.

Example 43 provides the method of Example 42 optionally furthercomprising bypassing the DEC in an economizer mode by closing thescavenger air inlet and directing the scavenger air to enter the firstportion at a location downstream of the DEC.

Example 44 provides the method of any of Example 42 or 43 optionallyfurther comprising passing the process air through a direct expansioncooling device arranged in the second portion of the conditioning systemdownstream of the AAHX, wherein the direct expansion cooling deviceprovides additional cooling to the process air exiting the AAHX.

Example 45 provides the method of Example 44 optionally furthercomprising passing the scavenger air through a condenser coil arrangedin the first portion of the conditioning system downstream of the AAHX,wherein the condenser coil cools the refrigerant from the directexpansion cooling device, using the scavenger air.

Example 46 provides the method of any of Examples 42-45 optionallyfurther comprising determining an operating mode of the conditioningsystem as a function of a set point temperature, wherein the set pointtemperature is compared to a measured temperature at the process airoutlet.

Example 47 provides the method of any of Examples 42-46 optionallyconfigured such that the first and second portions of the conditioningsystem are separate from each other such that the scavenger air and theprocess air pass through the conditioning system separately and remainas separate flow paths.

Example 48 provides the method of any of Examples 42-47 optionallyconfigured such that the process air at the process air inlet is hotaisle return air from a data center and the process air at the processair outlet is cold aisle supply air.

Example 49 provides the method of any of Examples 42-48 optionallyconfigured such that the first portion is a top level and the secondportion is a bottom level, and the conditioning system is configured asa roof-top delivery system.

Example 50 provides the method of any of Examples 42-48 optionallyconfigured such that the first portion and the second portion arearranged side-by-side, and the conditioning system is configured as anend-on delivery system for attachment to a side of a building.

Example 51 provides the method of any of Examples 42-50 optionallyconfigured such that the AAHX is a counter-flow flat plate heatexchanger configured for counter-parallel flow such that the flow pathof the scavenger air is in an opposite direction of the flow path of theprocess air.

Example 52 provides the method of any of Examples 42-50 optionallyconfigured such that the AAHX is a counter-flow flat plate heatexchanger configured for counter-cross flow such that the flow path ofthe scavenger air crosses the flow path of the process air inside theAAHX.

Example 53 provides a method, system, unit, product or apparatus of anyone or any combination of Examples 1-52, which can be optionallyconfigured such that all steps or elements recited are available to useor select from.

Various aspects of the disclosure have been described. These and otheraspects are within the scope of the following claims.

1. A system for controlling temperature in an enclosed space, the systemcomprising: a process air flow path having a process air inlet andoutlet; a set point temperature for the process air at the process airoutlet; a scavenger air flow path having a scavenger air inlet andoutlet, the scavenger air flow path and process air flow path separatefrom one another in the system; an air-to-air heat exchanger (AAHX)arranged in the process air flow path and in the scavenger air flowpath, the scavenger air conditioning the process air using the AAHX, theAAHX comprising at least one of a counter-flow flat-plate heat exchangerand a sensible wheel; a direct evaporative cooler (DEC) arranged in thescavenger air flow path between the AAHX and the scavenger air inlet,the DEC selectively conditioning the scavenger air prior to thescavenger air passing through the AAHX; and a direct expansion coolingdevice arranged in the process air flow path downstream of the AAHX, thedirection expansion cooling device selectively providing furtherconditioning of the process air exiting the AAHX, wherein an operatingmode of the system is selected from a plurality of operating modes basedon a comparison of a measured temperature at the process air outlet andthe set point temperature.
 2. The system of claim 1 wherein theplurality of operating modes includes a first mode of operation in whichonly the AAHX is needed to sufficiently condition the process air suchthat the measured temperature at the process air outlet is at or nearthe set point temperature.
 3. The system of claim 2 wherein the firstmode of operation includes bypassing the DEC and the direct expansioncooling device.
 4. The system of claim 1 wherein the plurality ofoperating modes includes a second mode of operation in which the AAHXand the DEC sufficiently condition the process air such that themeasured temperature at the process air outlet is at or near the setpoint temperature.
 5. The system of claim 4 wherein the second mode ofoperation includes bypassing the direct expansion cooling device.
 6. Thesystem of claim 1 wherein the operating mode includes a third mode ofoperation in which the direct expansion cooling device provides furtherconditioning of the process air exiting the AAHX, in addition toconditioning provided by the AAHX and the DEC.
 7. The system of claim 1wherein the direct expansion cooling device comprises: a DX coilarranged in the process air flow path between the AAHX and the processair outlet; and a condenser coil arranged in the scavenger air flow pathbetween the AAHX and the scavenger air outlet.
 8. The system of claim 1wherein the set point temperature is about 75 degrees Fahrenheit.
 9. Thesystem of claim 1 wherein the set point temperature includes anacceptable temperature range for the process air at the process airoutlet.
 10. The system of claim 9 wherein the acceptable temperaturerange is between about 75 and about 78 degrees Fahrenheit.
 11. A controlsystem for controlling a temperature of supply air delivered to anenclosed space, the control system comprising: a sensible wheel arrangedin a flow path of process air between a process air inlet and outlet andin a flow path of scavenger air between a scavenger air inlet andoutlet, the scavenger air conditioning the process air using thesensible wheel, the scavenger air flow path and process air flow pathseparated from one another in the system; a plurality of operating modesfor operating the system, an operating mode selected from the pluralityof operating modes based on a comparison of a measured temperature ofthe process air at the process air outlet to a set point temperature; adirect evaporative cooler (DEC) arranged in the scavenger air flow pathupstream of the sensible wheel, the direct evaporative coolerselectively conditioning the scavenger air prior to the scavenger airpassing through the sensible wheel depending on the selected operatingmode; and a DX coil arranged in the process air flow path downstream ofthe sensible wheel, the DX coil selectively conditioning the process airexiting the sensible wheel depending on the selected operating mode. 12.The control system of claim 11 further comprising a first bypass featurefor the scavenger air to bypass the DEC in a first operating mode. 13.The control system of claim 11 further comprising a second bypassfeature for the process air to bypass the DX coil in a first operatingmode and a second operating mode.
 14. The control system of claim LIfurther comprising a condenser coil arranged in the scavenger air flowpath between the sensible and the scavenger air outlet, the condensercoil configured to cool a refrigerant from the DX coil, using thescavenger air.
 15. A method for controlling a temperature of supply airdelivered an enclosed space, the method comprising: passing scavengerair and process air through an air-to-air heat exchanger (AAHX) arrangedin a conditioning system, the scavenger air passing through a firstportion of the conditioning system, the process air passing through asecond portion of the conditioning system separate from the firstportion, the AAHX arranged partially in the first portion and partiallyin the second portion, and the scavenger air cools the process air inthe AAHX; selectively passing the scavenger air through a directevaporative cooler (DEC) arranged in the first portion, depending on anoperating mode of the conditioning system; selectively passing theprocess air through a DX coil arranged in the second portion, dependingon the operating mode of the conditioning system; measuring atemperature of the process air at a process air outlet of the secondportion; comparing the measured process air temperature to a set pointtemperature of the process air at the process air outlet; anddetermining the operating mode of the conditioning system from amongfirst, second and third operating modes, the operating mode determinedas a function of a difference between the measured process airtemperature and the set point temperature,
 16. The method of claim 15wherein the first operating mode excludes operation of the DEC and DXcoil, the second operating mode excludes operation of the DX coil, andthe third operating mode includes operation of the AAHX, DEC and DXcoil.
 17. The method of claim 16 further comprising: directing theprocess air through the second portion such that the process airbypasses the DX coil in the first and second operating modes.
 18. Themethod of claim 16 further comprising: directing the scavenger airthrough the first portion such that the scavenger air bypasses the DECin the first operating mode.
 19. The method of claim 15 whereindetermining the operating mode of the conditioning system includesdetermining the lowest operating mode sufficient to adequately conditionthe process air such that the measured temperature at the process airoutlet is at or near the set point temperature.